Imaging system

ABSTRACT

An imaging system includes an imaging body having an optical system and an imaging element, a power supplier configured to supply power to the imaging element, and a housing configured to hold the imaging body and the power supplier, wherein the optical system includes at least one optical element projecting from the housing, and a distance AP between a gravity center A of a portion including the optical system and a gravity center P of the entire imaging system and a distance BP between a gravity center B of the power supplier and the gravity center P of the entire imaging system satisfy the following condition. 
       AP&gt;BP

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. application Ser. No.15/223,574, filed Jul. 29, 2016, which is a continuation of U.S.application Ser. No. 14/854,595 now U.S. Pat. No. 9,456,113), filed Sep.15, 2015, which is a continuation of U.S. application Ser. No.13/795,453 (now U.S. Pat. No. 9,185,279), filed Mar. 12, 2013, which isbased on and claims priority from Japanese Patent Application No.2012-060242, filed on Mar. 16, 2012, and Japanese Patent Application No.2012-277671, filed on Dec. 20, 2012, the disclosures of each of theabove are hereby incorporated by reference in their entirety.

BACKGROUND Field of the Invention

The present invention relates to an imaging system in which a lenssurface projects from a housing.

Description of the Related Art

An imaging system using a plurality of wide-angle lenses such as afisheye lens or a super-wide-angle lens is known as an imaging systemwhich images all directions at one time. In such an imaging system, animage from each lens is projected on the same or corresponding sensor,and the projected images are combined by an image process, so as toproduce an omnidirectional image.

When an imaging system is created with a small number of opticalcomponents, an angle of view assigned to each lens tends to beincreased. For example, when photographing an omnidirectional image byusing two fisheye lenses, each of the fisheye lenses requires a 180° ormore angle of view.

A wide-angle lens, however, tends to have a small curvature radius onthe incident side, and project from a housing. In an imaging system inwhich a lens surface projects from a housing, a lens is easily damagedwhen dropping the imaging system.

A technique described in Patent Document 1 (JP S62-191838A), forexample, is known as a technique which protects a lens from beingdamaged. Patent Document 1 discloses a camera with a lens cover in whicha push button for opening and closing a lens cover is provided in a sideface of a lens barrel cover on a grip side. Such a technique describedin Patent Document 1 requires the push button for opening and closing alens cover, resulting in an increase in costs.

In the above-described imaging systems, in particular, an imaging systemhaving a linear housing, an optical system, shutter button, and powersupplier are often linearly arranged. A photographer holds such animaging system between the gravity center of the imaging system and theposition of the shutter button. When the arrangement of an opticalsystem and a power supplier, which account for a substantial fraction ofthe weight of the imaging system, is inappropriate, camera shake easilyoccurs in the case of pushing the shutter button. It therefore becomesdifficult for a photographer to stably perform photographing.

SUMMARY

The present invention has been made in view of the above circumstances,and an object of the present invention is to provide an imaging systemin which a lens surface projects from a housing, and a balance of acenter of a gravity is improved.

Another object of the present invention is to provide an imaging systemin which a lens surface projects from a housing, and a possibility oflens surface damage in the case of dropping the imaging system ispreferably decreased without adding a new component.

In order to achieve the above objects, one embodiment of the presentinvention provides an imaging system including an imaging body having anoptical system and an imaging element, a power supplier configured tosupply power to the imaging element, and a housing configured to holdthe imaging body and the power supplier, wherein the optical systemincludes at least one optical element projecting from the housing, and adistance AP between a gravity center A of a portion including theoptical system and a gravity center P of the entire imaging system and adistance BP between a gravity center B of the power supplier and thegravity center P of the entire imaging system satisfy the followingcondition.

AF>BP

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide further understandingof the invention, and are incorporated in and constitute a part of thisspecification. The drawings illustrate embodiments of the invention and,together with the specification, serve to explain the principle of theinvention.

FIG. 1 is an overall view illustrating an omnidirectional imaging systemaccording to an embodiment of the present invention.

FIG. 2 is a detailed view illustrating two imaging optical systems in animaging body of the omnidirectional imaging system according to theembodiment of the present invention.

FIG. 3 is a view describing a sag amount in a first lens LA1, LA2.

FIG. 4 is an overall view illustrating an omnidirectional imaging systemaccording to another embodiment of the present invention.

FIG. 5 is an overall view illustrating an omnidirectional imaging systemaccording to another embodiment of the present invention.

FIG. 6 is view illustrating six planes of an omnidirectional imagingsystem according to another embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, embodiments of the present invention will be described.However, the present invention is not limited to the followingembodiments. In the following embodiments, an omnidirectional imagingsystem 10 including an imaging body having two fisheye lenses in anoptical system and a battery as a power supplier is described as oneexample of an imaging system.

FIG. 1 is an overall view illustrating the omnidirectional imagingsystem 10 according to the embodiment of the present invention. Theomnidirectional imaging system 10 illustrated in FIG. 1 includes animaging body 12, battery 14, controller boards 16A, 16B, and housing 18which holds these components 12, 14, 16A, 16B. In the embodimentillustrated in FIG. 1, the imaging body 12 includes two image-formingoptical systems 20A, 20B and two imaging elements 24A, 24B. An imagingoptical system is made of the combination of one image-forming opticalsystem 20 and one imaging element 24.

Each of the image-forming optical systems 20A, 20B illustrated in FIG. 1is constituted as a fisheye lens of seven elements in six groups. Thefisheye lens constituted by the image-forming optical system 20 includesan angle of view larger than 180°(=360°/n; n=2) in the embodimentillustrated in FIG. 1. It is preferable for the fisheye lens to includea 185° or more angle of view, and it is more preferable for the fisheyelens to include a 190° or more angle of view. With such an angle ofview, images are synthesized by an image process based on an overlappedarea.

FIG. 2 is a view illustrating the detailed configuration of the twoimage-forming optical systems 20A, 20B in the imaging body 12illustrated in FIG. 1. The image-forming optical systems 20A, 20B arecemented with the respective prisms as an axis as illustrated in FIG. 1.However, in FIG. 2, the two image-forming optical systems 20A, 20B areseparated for the sake of simplicity. As illustrated in FIG. 2, thefirst image-forming optical system 20A includes a front group havinglenses LA1-LA3, a right angle prism PA as a reflection member, and aback group having lenses LA4-LA7. An aperture stop SA is disposed on theobject side of the fourth lens LA4. In the first image-forming opticalsystem 20A, a filter F and an aperture stop SA are disposed on the imageside of the seventh lens LA7.

The image-forming optical system 20B includes a front group havinglenses LB1-LB3, a right angle prism PB, and a back group having lensesLB4-LB7. An aperture stop SB is disposed on the object side of thefourth lens LB4. A filter F and an aperture stop SB are disposed on theimage side of the seventh lens LB7.

In a specific embodiment, the lenses LA1-LA3 of the front group of thefirst image-forming optical system 20A are, in order form the objectside, a negative meniscus lens (LA1) made of an optical glass material,a negative lens (LA2) made of a plastic resin material, and a negativemeniscus leas (LA3) made of an optical glass material. The lensesLA4-LA7 of the back group are, in order from the object side, a biconvexlens (LA4) made of an optical glass material, a cemented lens of abiconcave lens (LA6) and a biconvex lens (LA5) made of an optical glassmaterial, and a biconvex lens (LA7) made of a plastic resin material.

In a specific embodiment, the lenses LB1-LB3 of the front group of thesecond image-forming optical system 20B are, in order from the objectside, a negative meniscus lens (LB1) made of an optical glass material,a negative lens (LB2) made of a plastic resin material, and a negativemeniscus lens (LB3) made of an optical glass material. The lensesLB4-LB7 of the back group are, in order from an object side, a biconvexlens (LB4) made of an optical glass material, a cemented lens of abiconcave lens (LB6) and a biconvex lens (LB5) made of an optical glassmaterial, and a biconvex lens (LB7) made of a plastic resin material.

In the first and second image-forming optical systems 20A, 20B, thenegative lenses LA2, LB2 in the front groups, which are made of aplastic resin material, and the biconvex lenses LA7, LB7 in the backgroups, which are made of a plastic resin material, have an asphericsurface on both surfaces. Each of the lenses made of an optical glassmaterial is a spherical lens.

It is preferable for each of the right angle prisms PA, PB disposedbetween the front group and the back group to be formed by a materialhaving a refractive index of d-line (λ=587.6 nm) larger than 1.8. Theright angle prism PA, PB internally reflects the light from the frontgroup toward the back group. The optical path of the imaging light beamtherefore passes through the right angle prism PA, PB in each of theimage-forming optical systems 20A, 20B. By constituting the right angleprism with a material having a high refractive index, the optical pathlength in the right angle prism PA, PB is increased, and the opticalpath length between the front group and the back group in the frontgroup, the right angle prism and the back group can be increased to belarger than the mechanical length. Thus, the fisheye lens can bedownsized.

By disposing the right angle prisms PA, PB near the aperture stops SA,SB, a right angle prism having a small outer diameter can be used, andthe distance between the fisheye lenses can be reduced. Moreover, byadopting the arrangement of the right angle prisms PA, PB as illustratedin FIG. 2, the parallax of the two optical systems can be reduced.Furthermore, by disposing the two image-forming optical systems to faceeach other as illustrated in FIGS. 1, 2, the imaging system can befurther downsized, and a non-imaging space can be reduced.

The optical elements (lens, prism, filter and aperture stop) of each ofthe two image-forming optical systems 20A, 20B are held by the lensbarrel 26 relative to each of the imaging elements 24A, 24B such thatthe optical axes of the optical elements are located orthogonal to thecentral portion of the light-receiving area of the corresponding imagingelement 24, and the light-receiving area becomes the imaging face of thecorresponding fisheye lens. Namely, each of the image-forming opticalsystems 20 is positioned such that an image of an imaging target isimaged in the light-receiving area of the corresponding imaging element24.

Each of the imaging elements 24 is a two-dimensional imaging element inwhich a light-receiving area forms an area, and converts the lightcollected by the corresponding image-forming optical system 20 in to theimage signals. Each of the imaging elements 24A, 24B includes aconfiguration in which tiny right-receiving areas are two-dimensionallyarranged on the light-receiving surface. The information, which isphotoelectrically converted in each of the tiny light-receiving areas,constitutes each pixel.

In the embodiment illustrated in FIG. 1, the image-forming opticalsystems 20A, 20B have the same specification, and are combined to beopposite to each other such that the optical axes are aligned. Theomnidirectional imaging system 10 is configured to image omnidirectionalimage information by combining the two image-forming optical systems20A, 20B and the two imaging elements 24A, 24B. By adopting theconfiguration illustrated in FIG. 1, an object above the housing 18 canbe photographed.

The image obtained by the first image-forming optical system 20A isimaged on the light-receiving area of the two-dimensional imagingelement 24A. The image obtained by the second image-forming opticalsystem 20B is also imaged on the light-receiving area of thetwo-dimensional imaging element 24B. The imaging elements 24A, 24Bconvert the received light distribution into the image signals to beinput to the controller boards 16A, 16B.

A not-shown image processor and output unit are provided on thecontroller boards 16A, 16B. The image signals output from the imagingelements 24A, 24B are input to the image processor on the controllerboard 16. The image processor synthesizes the image signals input fromthe imaging elements 24A, 24B into one image to obtain an image of solidangle of 4π radian (hereinafter referred to as an omnidirectionalimage), and outputs the image to the output unit. In the embodimentillustrated in FIG. 1, an omnidirectional image is formed, but aso-called panoramic image in which 360° only in a horizontal plane isphotographed can be formed.

As described above, since the fisheye lens includes a 180° or more angleof view, the overlapped image portion is used as a reference forcombining the images as standard data showing the same image whenforming an omnidirectional image by-synthesizing image signals outputfrom the imagine elements 24A, 24B. The output unit is, for example, adisplay device, printer, or external memory such as an SD card orcompact flash (registered trademark), and outputs the synthesizedomnidirectional image.

The battery 14 is a power supplier which supplies power to a chip or acomponent on the controller boards 16A, 16B and the imaging elements24A, 24B. The battery 14 is a primary battery such as an alkalinemanganese primary battery or oxyride primary battery, or a secondarybattery such as a lithium ion secondary battery, lithium ion polymersecondary battery or nickel hydride secondary battery.

The omnidirectional imaging system 10 illustrated in FIG. 1 includes abar shape having one end provided with the image-forming optical system.The housing 18 includes a main body holding a module including thecontroller boards 16A, 16B and the battery 14, and a lens holder holdingthe imaging body 12 and provided with an opening from which the firstlenses LA1, LB1 are exposed. The housing 18 includes flat housing faces18A, 18B of the main body.

In the image-forming optical systems 20A, 20B illustrated in FIG 1, thefirst lenses LA1, LB1 located on the most object side project from thehousing faces 18A, 18B in the main body of the housing 18. In a specificembodiment, the first lenses LA1, LB1 are exposed outside the housing18.

When the first lenses LA1, LB1 are made of an optical glass material,the lens surfaces may get cracked under a dropping condition from aheight of about 1.5 m in a dropping test of the imaging optical system20A. When the first lenses LA1, LB1 are made of a plastic resinmaterial, the lens surfaces may be scratched under a dropping conditionsimilar to the above. Namely, when a photographer drops theomnidirectional imaging system 10 by accident, the first lens may bedamaged. When the first lenses LA1, LB1 are damaged, an image cannot beappropriately formed on the light-receiving surface of the imagingelement 24; thus, it becomes difficult to obtain a preferable image.

The above-described imaging body 12 and the battery 14 are main memberswhich account for a substantial fraction of the weight of theomnidirectional imaging system 10 illustrated in FIG. 10. For thisreason, the omnidirectional imaging system 10 according to the presentembodiment includes the following features regarding the arrangement ofthe imaging body 12 and the battery 14 as the main members, whichaccount for a substantial fraction of the weight of the omnidirectionalimaging system 10, based on the moment of the entire omnidirectionalimaging system 10.

In the omnidirectional imaging system 10, a distance AP between agravity center A of the imaging body 12 and a gravity center P of theentire omnidirectional imaging system 10 and a distance BP between agravity center B of the battery 14 and the gravity center P of theentire omnidirectional imaging system 10 satisfy the following condition1.

AP>BP  (Condition 1)

By satisfying the above condition 1, the gravity center P of the entireomnidirectional imaging system 10 is biased on the battery 14 side. Withthis configuration, when the omnidirectional imaging system 10 isdropped from a hand, for example, a possibility that the omnidirectionalimaging system 10 drops from the side of the imaging body 12 having theprojected optical elements can be decreased.

In a preferred embodiment, a shutter button can be disposed in aposition S between the gravity center A of the imaging body 12 and thegravity center P of the entire omnidirectional imaging system 10. Theshutter button is an input unit for starting imaging, which is pushed bya photographer for inputting an instruction to start imaging. It ispreferable for the imaging body 12, shutter button and battery 14 to bearranged on the same straight line x in order of the gravity center A ofthe imaging body 12, the position S of the shutter button and thegravity center P of the entire omnidirecional imaging system 10. Theshutter button is arranged on the front face of the housing 18.

The arrangement of the shutter button is not limited to the arrangementillustrated in FIG. 1. FIG. 5 is an overall view illustrating anomnidirectional imaging system 10 according to another embodiment. Inthe omnidirectional imaging system 10 illustrated in FIG. 5, the shutterbutton 22 is located on the left side of the straight line x, namely,below the left side of the image-forming optical system 20. Similar tothe arrangement in FIG. 1, the gravity center A of the imaging body 12,the position S of the shutter button and the gravity center P of theomnidirectional imaging system 10 are arranged in order of the gravitycenter A, the position S and the gravity center P. FIG. 6 is a viewillustrating six planes of the omnidirectional imaging system 10according to another embodiment.

In order to stably hold the omnidirectional imaging system 10, it ispreferable for a photographer to hold the omnidirectional imaging system10 near the center N of the shape the omnidirectional imaging system 10,namely, between the position S and the position P. A photographer pushesthe shutter button deposed on the imaging body 12 side of the gravitycenter P with the above-described held condition. In this case, byadopting the arrangement in which the gravity center P is biased on thebattery 14 side away from the imaging body 12, camera shake which causesa deterioration in an image quality is controlled because the moment onthe battery 14 side is larger even if the shutter button is pushed. Aphotographer therefore stably photographs an image by using theomnidirectional imaging system 10.

In addition, the three dimensional gravity center of each of the members12, 14 can be specified by measuring the gravity center in thetwo-dimensional direction of each of the members multiple times by usinga load cell (mass-measuring instrument). In the embodiment, the gravitycenter A is the gravity center of the entire imaging body 12 includingthe two image-forming optical systems 20A, 20B, lens barrel 26 andimaging elements 24A, 24B. However, in another embodiment, the gravitycenter of the portion including the two image-forming optical systems20A, 20B and the lens barrel 26 without including the imaging elements24A, 24B can be the gravity center A. In addition, the gravity center Bis the gravity center of the battery 14 without including a cable whichconnects the battery 14 to the imaging element 24 in this embodiment.

In the omnidirectional imaging system 10, it is preferable for a weightm of the imaging body 12 and a weight M of the battery 14 to satisfy thefollowing condition 2.

m<M  (Condition 2)

In the omnidirectional imaging system 10, it is preferable for theweight m of the imaging body 12, the weight M of the battery 14, adistance AN between the gravity center A of the imaging body 12 and thecenter N of the shape of the entire omnidirectional imaging system 10,and a distance BN between the gravity center B of the battery 14 and thecenter N to satisfy the following condition 3.

m×AN<M×BN  (Condition 3)

By satisfying the above conditions 2, 3, the gravity center P of theentire omnidirectional imaging system 10 is biased on the battery 14side. With this configuration, when the omnidirectional imaging system10 drops from a hand, for example, a possibility that the imaging system10 is dropped from the side of the imaging body 12 having the projectedoptical elements can be decreased.

The above described arrangement is especially effective for an imagingsystem in which the first lenses LA1, LB1 project from the housing faces18A, 18B, and also especially effective for an imaging system in whichthe sag amount of the first lenses LA1, LB1 becomes 3 mm or more. Thisis because cracking becomes remarkable in a lens made of an opticalglass material and scratching becomes remarkable in a lens made of aplastic resin material in the dropping test from 1.5 m when the sagamount of the first lenses LA1, LB1 becomes 3 mm or more. In addition,the sag amount shows a sag amount in an effective diameter, and does notinclude a sag amount of a non-effective diameter.

The above sag amount h is defined as illustrated in FIG. 3. It ispreferable for a curvature radius r of the convex lens of the first lensLA1, LB1 and an effective diameter (diameter) R of the first lens LA1,LB1 to satisfy the following condition 4 by normalizing with thecurvature radius r.

1−1 cos {sin⁻¹(R/2r)}≧0.17  (Condition 4)

For example, when the curvature radius r of the convex lens of the firstlens LA1, LB1 is 18 mm and the effective diameter R of the first lensLA1, LB1 is 20 mm, the sag amount h of the first lens becomes about 3.03mm, and the value (h/r) in which the sag amount h is normalized by thecurvature radius r becomes about 0.17. The above condition 4 thereforeis satisfied.

Moreover, when the curvature radius r of the convex lens of the firstlens LA1, LB1 is 17 mm and the effective diameter R of the first lensLA1, LB1 is 20 mm, the sag amount h of the first lens becomes about 3.25mm, and the value (h/r) in which the sag amount h is normalized by thecurvature radius r becomes about 0.19. The above condition 4 thereforeis satisfied.

Furthermore, when the curvature radius r of the convex lens of the firstlens LA1, LB1 is 10 mm and the effective diameter R of the first lensLA1, LB1 is 20 mm, the sag amount h of the first lens becomes about10.00 mm, and the value (h/r) in which the sag amount h is normalized bythe curvature radius r becomes about 1. The above condition 4 thereforeis satisfied. In addition, the upper limit of the normalized value (h/r)is 1.

Hereinafter, a material for achieving the arrangement of the imagingbody 12 and the battery 14 satisfying the above conditions 1-3 will bedescribed.

In order to reduce the weight m of the imaging body 12 to be lower thanthe weight M of the battery 14, namely, to satisfy the above condition3, a material having a small specific gravity is adopted for the lensfor use in the image-forming optical system 20 of the imaging body 12.As described above, the image-forming optical system 20 includes sevenlenses in six groups according to a specific embodiment. In such aconfiguration, the second lens LA2, LB2 from the object side and theseventh lens LA7, LB7 from the object side are made of a plastic resinmaterial. In another embodiment, the plastic resin material is notlimited to the second lens LA2, LB2 and the seventh lens LA7, LB7, andall or a part of the lenses LA1-LA7, LB1-LB7 can be made of a plasticresin material.

It is preferable for the material of the lens to use a plastic resinmaterial having a specific gravity of 2.5 g/cm³ or below (unit will behereinafter omitted). Such a plastic resin material includes cycloolefinresin (specific gravity 1.1), episulfide series resin (specific gravity1.46), thiourethane series resin (specific gravity 1.35), (polyester)methacrylate (specific gravity 1.37), polycarbonate (specific gravity1.20), (urethane) methacrylate (specific gravity 1.17), (epoxy)methacrylate (specific gravity 1.19), diallyl carbonate (specificgravity 1.23), diallyl phthalate series resin (specific gravity 1.27),methane series resin (specific gravity 1.1), polymethylmethacrylate(specific gravity 1.18) and allyl diglycol carbonate (specific gravity1.32). It is more preferable for the material of the lens to use aplastic resin material having a specific gravity of 1.1 or more and lessthan 1.25 such that the specific gravity is decreased twice or more thespecific gravity (2.5) of glass.

In order to satisfy the above condition 3, it is also preferable for thematerial of the lens barrel 26 holding a lens to use a material having asmall specific gravity. It is preferable for the material of the lensbarrel to use a plastic resin material having a specific gravity smallerthan 2.7 g/cm³. A complex material of resin such as polycarbonate resin(PC), polyphenylene sulfide resin (PPS), acrylonitrile butadiene styreneresin (ABS), polybutylene terephthalate (PBT), polvethyleneterephthalate resin (PET), polystyrene resin (PS), polyphenyleneetherresin (PPE), and polyamide resin (PA), and filler such as glass fiber,carbon fiber, and carbon fiber, for example pitch series or PAN(polyacrylonitrile) series can be used as the plastic resin material ofthe lens barrel.

It is more preferable for the plastic resin material of the lens barrelto use a plastic resin material having a specific gravity of 1.3 or moreand less than 1.35 which is decreased twice or more the specific gravity(2.7) of aluminum. A polycarbonate material with glass can be used asthe material for forming the lens barrel.

As illustrated in FIG. 1, the onmidirectional imaging system 10 includesan impact absorber 30. The impact absorber is provided near the battery14 in the exterior of the housing 18. A low-modulus rubber material suchas low resilient urethane rubber or an impact absorbing gel moldedmaterial can be used for the impact absorber.

With the above-described arrangement, when the omnidirectional imagingsystem 10 is dropped from a hand, the imaging system 10 tends to dropfrom the battery 14 side. The housing 18 and the module can be protectedin such dropping by the impact absorber 30.

In the above embodiment, the omnidirectional imaging system which canphotograph all directions by using the two imaging optical systems isdescribed. However, the embodiment is not limited to the combination ofthe two imaging optical systems, and it can be applied to a monocularbar type camera. In the above description, the fisheye lens in which thedistortion is not corrected is described as one example, but theomnidirectional imaging system can be constituted by using asuper-wide-angle lens in which the distortion is corrected.

Moreover, the above embodiment can be applied to an imaging system whichcan photograph all directions by using n-imaging optical systems where nis a natural number larger than 2. For example, an imaging system can beconstituted by radially disposing three wide-angle lenses (image-formingoptical system) having an angle of view larger than 360°/3=120° in thesame plane, and combining the lenses with imaging elements,respectively. An image to be obtained with this system is not anomnidirectional image, but such a system can image a horizontalpanoramic image of 360°, and is preferable for a car-mounted camera orsecurity camera. The image can be a still image or moving image.

In the above embodiment, the omnidirectional imaging system having alinear shape is described. However, the above-described arrangement canbe applied to an omnidirectional imaging system having another shape.FIG. 4 is a view illustrating an entire omnidirectional imaging systemaccording to another embodiment. In addition, since an omnidirectionalimaging system 50 according to the embodiment illustrated in FIG. 4includes a configuration similar to that of the omnidirectional imagingsystem 10 of the embodiment illustrated in FIG. 1, differences betweenthe embodiment illustrated in FIG. 1 and the embodiment illustrated inFIG. 4 will be mainly described in the following description.

The omnidirectional imaging system 50 according to another embodimentillustrated in FIG. 4 includes an imaging body 52, battery 54, not-showncontroller board, and housing 58 which holds these components. In theembodiment illustrated in FIG. 4, the imaging body 52 includes twoimage-forming optical systems as a fisheye lens having seven lenses insix groups and two imaging elements similar to the embodimentillustrated in FIG. 1. The image-forming optical system illustrated inFIG. 4 includes a configuration similar to the embodiment illustrated inFIGS. 1, 2, but does not have a right angle prism between the frontgroup and the back group, and the image-forming optical systems arecombined to be opposite to each other with their optical axes aligned.

The omnidirectional imaging system 50 illustrated in FIG. 4 includes aspherical shape provided with an imaging optical system on both sides.The housing 58 includes a main body which holds the imaging body 52,controller board and battery 54. An opening from which the first lensesLA1, LB2 are exposed is provided in the main body of the housing 58. Inthe image-forming optical system illustrated in FIG. 4, the first lensesLA1, LB2 located on the most object side project from the surface of thehousing 58 and are exposed outside the housing 58.

Similar to the omnidirectional imaging system 10 illustrated in FIG. 4,the imaging body 52 and the battery 54 become the main members whichaccount for a substantial fraction of the weight of the omnidirectionalimaging system 50 illustrated in FIG. 4. In this case, in theomnidirectional imaging system 50 according to the embodimentillustrated in FIG. 4, the arrangement of the imaging body 52 and thebattery 54 of the main members which account for a substantial fractionof the weight of the omnidirectional imaging system 50 has the followingfeature.

In the omnidirectional imaging system 50 according to another embodimentillustrated in FIG. 4, a distance AP between a gravity center A of theimaging body 52 and a gravity center P of the entire omnidirectionalimaging system 50 and a distance BP between a gravity center B of thebattery 54 and the gravity center P of the entire omnidirectionalimaging system 50 satisfy the above condition 1.

By satisfying the above condition 1, the gravity center P of the entirespherical omnidirectional imaging system 50 illustrated in FIG. 4 isbiased on the battery 54 side as the omnidirectional imaging system 10illustrated in FIG. 1. Moreover, by providing an impact absorber 70 nearthe battery 54 in the exterior of the housing 58, the housing 58 can bepreferably protected in dropping.

Since a condition which defines another arrangement is similar to thatillustrated in FIG. 1, the detailed description thereof will be omitted.

As described above, according to the embodiments of the presentinvention, an imaging system in which the lens surface projects from thehousing, and the balance of the gravity center is improved can beprovided. In addition, in the imaging system, a possibility of lenssurface damage when dropping the imaging system can be preferablydecreased without adding a new member.

Hereinafter, the imaging system according to the embodiments of thepresent invention will be described in details by using the followingEmbodiments. However, the present invention is not limited to thefollowing Embodiments.

Embodiment 1

The omnidirectional imaging system 10 having a linear shape illustratedin FIG. 1 was obtained. Each of the image-forming optical systems 20A,20B had seven lenses in six groups. In this confirmation, the secondlens LA2, LB2 from the object side and the seventh lens LA7, LB7 fromthe object side were a plastic lens. The plastic lens was formed byusing a plastic resin material (specific weight 1.1) of E48R of Zeonex(registered trademark). The lens barrel 26 was formed by using apolycarbonate (PC+GF) material with glass having a specific weight of1.3.

The curvature radius r and the effective diameter R of the first lensLA1, LB1 were 17 mm and 20 mm, respectively, and the sag amount h of thefirst lens LA1, LB1 was about 3.25 mm. The projection amount of thefirst lens LA1, LB1 from the housing surface 18A, 18A was about 5 mm.The above condition 4 therefore was satisfied.

Measuring the gravity center A of the imaging body 12 in which thelenses LA1-7, LB1-7, right angle prisms PA, PB, lens barrel 26 andimaging elements 24A, 24B were combined, the gravity center P of theentire imaging system 10 and the gravity center B of the battery 14, thedistance AP was 38 mm, and the distance BP was 26 mm. The weight m ofthe imaging body 12 was 17 g and the weight M of the battery 14 was 25g. Moreover, measuring the distance AN between the gravity center A ofthe imaging body 12 and the center N of the shape of the omnidirectionalimaging system 10 and the distance BN between the gravity center B ofthe battery 14 and the center N of the form of the omnidirectionalimaging system 10, the distance AN was 35 mm and the distance BN was 29mm. The above conditions 1-3 therefore were satisfied.

The shutter button was provided in the position S in which the distancePS becomes 10 mm. Even when the shutter button in the position S waspushed by the pushing force of 10 g, the photographing was stablyperformed.

Embodiment 2

The omnidirectional imaging system 50 having a spherical shapeillustrated in FIG. 4 was obtained. Each of the image-forming opticalsystems had seven lenses in six groups. In this configuration, thesecond lens LA2, LB2 from the object side and the seventh lens LA7, LB7from the object side were a plastic lens of E48R of Zeonex (registeredtrademark). The lens barrel 26 was formed by using a polycarbonate(PC+GF) material with glass.

The curvature radius r and the effective curvature radius R of the firstlens LA1, LB1 were 17 mm and 20 mm, respectively, and the sag/amount hof the first lens LA1, LB1 was about 3.5 mm. The above condition 4therefore was satisfied.

Measuring the gravity center A of the imaging body 52 in which thelenses LA1-7, LB1-7, right-angle prisms PA, PB, lens barrel and imagingelements were combined, the gravity center P of the entire imagingsystem 50 and the gravity center B of the battery 54, the distance APwas 15 mm, and the distance BP was 10 mm. The weight m of the imagingbody 52 was 17 g and the weight M of the battery 54 was 25 g. Thedistance AN was 0 mm and the distance BN was 25 mm. The above conditions1-3 therefore were satisfied.

Embodiment 3

The omnidirectional imaging system 10 having a linear shape illustratedin FIGS. 5, 6 was obtained by using the lens barrel 26 and theimage-forming optical systems 20A, 20B similar to Embodiment 1. Thecurvature radius r and the effective diameter R of the first lens LA1,LB1 were 17 mm and 20 mm, respectively, and the sag amount h of thefirst lens LA1, LB1 was about 3.25 mm. The projection amount of thefirst lens LA1, LB1 from the housing surface 18A, 18A was about 5 mm.The above condition 4 therefore was satisfied.

Measuring the gravity center A of the imaging body 12 in which thelenses LA1-7, LB1-7, right angle prisms PA, PB, lens barrel 26 andimaging elements 24A, 24B were combined, the gravity center P of theentire imaging system 10 and the gravity center B of the battery 14, thedistance AP was 47 mm, and the distance BP was 32 mm. The weight m ofthe imaging body 12 was 17 g and the weight M of the battery 14 was 25g. Moreover, measuring the distance AN between the gravity center A ofthe imaging body 12 and the center N of the shape of the omnidirectionalimaging system 10 and the distance BN between the gravity center B ofthe battery 14 and the center N of the form of the omnidirectionalimaging system 10, the distance AN was 42 mm and the distance BN was 37mm. The above conditions 1-3 therefore were satisfied. The shutterbutton 22 was provided in the position S of the housing surface on thelens forming side in which the distance PS becomes 7.5 mm. Even when theshutter button in the position S was pushed by the pushing force of 10g, the photographing was stably performed.

Although the embodiments of the present invention have been describedabove, the present invention is not limited thereto. It should beappreciated that variations may be made in the embodiments described bypersons skilled in the art without departing from the scope of thepresent invention.

What is claimed is:
 1. An imaging system, comprising: an imaging bodyincluding an optical system and an imaging element; a power supplierconfigured to supply power to the imaging element; and a housingconfigured to hold the imaging body and the power supplier, wherein theoptical system includes at least one optical element projecting from thehousing, and a distance AP between a gravity center A of a portionincluding the optical system and a gravity center P of the entireimaging system and a distance BP between a gravity center B of the powersupplier and the gravity center P of the entire imaging system satisfythe following condition.AP>BP